How I spent my morning at SICB

Here's what I heard this morning. Wonderful stuff, all of it, and I'm having a grand time. This is a quick summary, and now I have to rush back to the meeting for more.

  • S. Kuratani: Craniofacial evolution from a developmental perspective. This was a lamprey and hagfish talk, comparing them to vertebrates. Hox gene expression patterns in lamprey, which assign anterior-posterior positional information, are very similar to those in vertebrates, but there is no temporal colinearity—timing is all over the place. There is no apparent dorsal-ventral patterning of Dlx gene expresion. They've collected a small number of hagfish eggs and embryos and gotten good histology (unlike much of the older work). The neural crest forms by delamination and migrates into the intersegmental spaces; it also looks very much like the vertebrate pattern.

  • A. Abzhanov: Pecking at the origin of avian morphological variation. This was the story recently published in Nature on the molecular basis of beak shapes in the Galapagos finches. In short, Bmp4 expression is important in regulating the width and depth of the beak, and Calmodulin expression affects the length; there is modularity in controlling the different beak dimensions. He promises to look in the future at a couple of different phenomena: a finch with a deep but narrow beak might help sort out the factors involved in those two dimensions, he's examining Galapagos mockingbirds, and he's looking at muscle-bone coupling, since muscles have to follow changes in bone structure.

  • J. Helms: Unraveling the basis for species specific facial form. More birds! Here the question is the role of differences in neural crest potential that affect beak/face morphology. In some cool transplant experiments, she put neural crest from a duck embryo (long, flat bill) into a quail (short, pointy beak), and found that the quail embryos from flatter, broader bills. The converse experiment, quail neural crest into a duck embryo, produced duck embryos with short, pointed beaks. Microarray analysis of the genes with differential patterns of expression in these two species revealed that the gene differences were turned on at the phylotypic stage, when the facial prominences were indistinguishable, and the gene expression patterns at the phenotypic stage were simply maintained or held over — there is a hidden variation at the phylotypic stage that precedes the morphological differentiation. She also showed some promising work for the future, looking at the molecular basis for beak variation in different breeds of pigeons.

  • Y. Yamamoto: Why cavefish lost their eyes? Natural selection or neutral theory. Hey, get the latest issue of Seed — I summarized this story already! Even shorter summary: it's indirect selection for a pleiotropic tradeoff.

  • G. Schlosser: How old genes make a new head: recent insights into development and evolution of neural crest and placodes in vertebrates. This is a neat little story about structural innovations in the evolution of the head. In addition to brain and ectoderm in the head, you've got two other in-between populations of plastic and critical cells: the neural crest, migratory cells that contribute to a host of tissues, and placodes, or ectodermal thickenings, that form structures like ears, lenses, lateral lines (if you had a lateral line), etc. Both populations arise at the neural plate boundary. One evolutionary scenario is that the boundary population appeared first, and then later subsets specialized to form neural crest and placodes; this model emphasizes a common origin for both. Schlosser presented his evidence and argument that they were unique from the beginning: placods are derived from the ectodermal side of the boundary, while neural crest are from the neural side.

  • L.Z. Holland: Heads or tails? Amphioxus and the evolution of axial patterning in chordates. This was a very thorough summary of comparative patterns of early gene expression in Amphioxus and frogs, fish, and all those other excessively complicated derived forms. She made the case that in many ways Amphioxius is a basal chordate. and that it has great advantages for studying axis formation and gastrulation: cell movements are minimal and simple, and you can see gene expression domains untangled from all the smearing of the extensive cell movements we see in, for instance, a frog. Among the interesting conclusions are the idea that differential Wnt gene expression is instrumental in specifying the anterior and posterior ends of the animal, and that gradients of retinoic acid (which directly target Hox gene expression) sets up positional information along the A/P axis in between.

  • G.P. Wagner: Linking the evolution of genes with the evolution of morphological characters. This was the first of two talks that set a different tone. Wagner pointed out that the developmental approach favored so far is excellent for sorting out what genes affect what other genes and are associated with the morphological differences that arise during development, but that they don't tell you what the molecular correlates of those differences are: what specifically are the sequence changes in the sonic hedgehog gene or its regulators that cause expansion of its domain in blind cavefish? He argued that evolutionary genetics can identify candidate molecular differences as part of a program of working out the precise details of evolutionary/developmental change. Readers of Carroll's work and its emphasis on the importance of cis regulatory elements will be interested that Wagner goes the other way, and is much more interested in the evolution of transcription factors. He gave a couple of reasons: 1) the specificity of gene regulation arises from protein-protein interactions in regulatory complexes. While there is much emphasis on the conserved sites that bind DNA in an individual protein, that is a small part of the whole, and these proteins are often poorly conserved out in the 80% that doesn't stick to DNA, but contacts other proteins. 2) Changes in these proteins change functionality in the organims in evolution. 3) There is evidence of directional selectivity in transcription factors. 4) It's much easier to work with sequences that are actually expressed (ah, pragmatism!). In detail, he discussed the Hoxa13 gene in zebrafish, which has been duplicated again in teleosts into Hoxa13a and Hoxa13b forms. The Hoxa13a gene is associated with a quirky morphological feature of the cypriniform fish that we zebrafish people are familiar with, the caudal extension of the yolk sac. It's an easily assayed feature, and Wagner showed that morpholino knockdowns of Hoxa13a cleanly suppressed yolk sac extension.

  • Lark G: Links between the genetic architecture and functional morphology of the canid skeleton. This talk was a radical break from the previous ones, and was almost purely genetics. I confess, I was starving and worn out and had to make a break for lunch, so I didn't give this talk the attention it deserved or needed, but I'll be looking into it later. Lark is looking at quantitative trait loci in Portuguese Water Dogs and the Red Fox, and arguing that there are conserved patterns of variability that have survived 10 million years of diverging evolution.

Oh, yeah, I think we're doing a panel discussion about science media sometime today. I have heard that it's at 4:00, but I think that's wrong: the short outline of events lists a Media Workshop (I think that's us!) from 7 to 9pm in the Curtis Room at the Hyatt. I'll start panicking right after the science sessions end this afternoon and run around and find out what's what, when, and where. They can't start without me, can they? GrrlScientist wouldn't abandon me, but I don't know about that sneaky Lynch fellow.

More like this

So you get to sit around all day listening to science and what do we get? A synopsis of that science stuff.
Where's the beef?
I need my creationist thumpin' on a daily basis. Please stay up all night and instead of drinking beer, post my fix !!!

That was weird. Sorry.

Man, I miss going to conferences as a delegate. Standing at a booth and hoping that people will at least acknowledge your presence while they steal your pens is not as much fun. Bigger expense accounts though.

By VancouverBrit (not verified) on 04 Jan 2007 #permalink

Sounds like an interesting set of talks.

Because of the role of cranial neural crest in the development of the thymus, thyroid, adrenal medulla, and other tissues, elucidation of its origins and diversification will greatly enhance the understanding of vertebrate neuroendocrine evolution and plasticity.

(AtBC afdavey "joke," sorry:)
Did Lark have anything to say about AiG's supposed "baboon dogs"?

Just, y'know, trying to be "charitable"...

By Steviepinhead (not verified) on 04 Jan 2007 #permalink

Looking at that list, I don't think you covered enough...

By BlueIndependent (not verified) on 04 Jan 2007 #permalink

Maybe I'm totally mixed up here but aren't hagfish and lampreys vertebrates themselves?

Maybe I'm totally mixed up here but aren't hagfish and lampreys vertebrates themselves?

Lampreys are often classified as craniata. The vertebrates are within the craniata but the lampreys are outside of that clade. (There are probably those who would disagree)

help sort out the factors involved in those two dimensions, he's examining Galapagos mockingbirds, and he's looking at muscle-bone coupling, since muscles have to follow changes in bone structure.

Well, yes, but bone shape is also a function of muscle forces. In other words, while the genetic variation could be coupled, or "co-evolved" it may also be that this is not necessary (and thus unlikely) within a certain range of difference.

Of course no one knows this, which is why it is good that he is looking at this.

....patterns of early gene expression in Amphioxus and frogs, fish, and all those other excessively complicated derived forms.

Yes, your slur is understood. And it stings all of us who study things with bones.

But, if a "A frog is a fish trying desparately to remain a fish" then EVERYTHING that is not a bacterium is a bacterium desparately trying to remain a bacterium.

So invertophiles really have nothing on vertophiles...

Oh, the news you're missing out on: Giant jellyfish attack Norway

Yes, but did you see the story right after that one on the same web site?

Giant squid seems built for speed (December 23, 2006) -- A breakthrough

I wonder if there is a connection. And if so, which one is swimming away from the other.

So, you are not going to any of the lectures on the newest Intelligent Design research that undoubtful must be there.

By Kristjan Wager (not verified) on 05 Jan 2007 #permalink


I have a question from the perspective of relatively ignorant about developmental biology. The question is fairly simple; how do we know that the morphological changes in Darwin's finches are the result of Natural Selection (operating on changes induced by BMP4 and making use of plasticity) and not solely phenotypic plasticity?

The reason I ask is that I'm seeing a creationist who argues that what we think of as examples of selection are actually simply examples of phenotypic plasticity (he advocates Lamarkism FYI). This isn't really my area and I thought you might be able to help